My application uses asynchronous calls. JMeter doesn't support that feature.
I had looked across NeoLoad(NeoTys), JMeter, Grinder, Stress Tester, Open Web Load, Load Runner but in vain.
I am using Linux OS ( I can't move over to windows.. -- company requirements). This is a main blocker.
I am looking for a load testing tool that would enable me to record and dynamically change values to implement the load test.

I'm Paul from Neotys. Did you ask our support about your tests with NeoLoad?
NeoLoad controller is available on Linux and Unix as well. We'll be pleased to investigate further with you. You can contact us on http://www.neotys.com/support/contact.html